#include <iostream>

using namespace std;
namespace MySpace
{
    extern int add(int x, int y, int z = 0);
    extern double add(double x, int y);
    extern double add(int x, double y);
    extern double add(double x, double y);
};

int main(void)
{
    using MySpace::add;
    cout << add(15, 20) << endl;
    cout << add(15, 20, 25) << endl;
    cout << add(15.15, 20.15) << endl;
    cout << add(15.15, 20) << endl;
    cout << add(15, 20.15) << endl;
}